Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.41	3.344%	$196.7773	$196.78	$196.80	$196.80
Purchase #2	$37.36	11.508%	$41.6594	$41.66	$41.65	$41.70
Purchase #3	$49.29	7.718%	$53.0942	$53.09	$53.10	$53.10
Purchase #4	$115.54	6.616%	$123.1841	$123.18	$123.20	$123.20
Purchase #5	$21.57	5.249%	$22.7022	$22.70	$22.70	$22.70
Purchase #6	$40.62	12.745%	$45.797	$45.80	$45.80	$45.80
Purchase #7	$211.48	6.335%	$224.8773	$224.88	$224.90	$224.90
7 purchase totals =	$666.27		$708.0915	$708.09	$708.15	$708.20